Question

我正在尝试在表单中键入一些信息并将其保存到数据库中。但是，当我按下我的应用程序中的“保存”按钮时，它会给我以下错误。

我的logcat

07-21 13:41:08.162: E/AndroidRuntime(6190): FATAL EXCEPTION: main
07-21 13:41:08.162: E/AndroidRuntime(6190): java.lang.NullPointerException
07-21 13:41:08.162: E/AndroidRuntime(6190):     at sp.com.DetailForm$1.onClick(DetailForm.java:110)
07-21 13:41:08.162: E/AndroidRuntime(6190):     at android.view.View.performClick(View.java:4243)
07-21 13:41:08.162: E/AndroidRuntime(6190):     at android.view.View$PerformClick.run(View.java:17520)
07-21 13:41:08.162: E/AndroidRuntime(6190):     at android.os.Handler.handleCallback(Handler.java:725)
07-21 13:41:08.162: E/AndroidRuntime(6190):     at android.os.Handler.dispatchMessage(Handler.java:92)
07-21 13:41:08.162: E/AndroidRuntime(6190):     at android.os.Looper.loop(Looper.java:153)
07-21 13:41:08.162: E/AndroidRuntime(6190):     at android.app.ActivityThread.main(ActivityThread.java:5299)
07-21 13:41:08.162: E/AndroidRuntime(6190):     at java.lang.reflect.Method.invokeNative(Native Method)
07-21 13:41:08.162: E/AndroidRuntime(6190):     at java.lang.reflect.Method.invoke(Method.java:511)
07-21 13:41:08.162: E/AndroidRuntime(6190):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:833)
07-21 13:41:08.162: E/AndroidRuntime(6190):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:600)
07-21 13:41:08.162: E/AndroidRuntime(6190):     at dalvik.system.NativeStart.main(Native Method)

我的DetailForm

package sp.com;

import android.app.Activity;
import android.content.Context;
import android.content.Intent;
import android.content.SharedPreferences;
import android.content.SharedPreferences.Editor;
import android.media.MediaPlayer;
import android.net.Uri;
import android.os.Bundle;
import android.preference.PreferenceManager;
import android.widget.Button;
import android.widget.TextView;
import android.util.Log;
import android.view.Menu;
import android.view.MenuInflater;
import android.view.MenuItem;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.AdapterView;
import android.widget.CheckBox;
import android.widget.EditText;
import android.widget.ImageButton;
import android.widget.RadioGroup;
import android.widget.Toast;
import java.util.ArrayList;
import java.util.List;
import android.app.TabActivity;
import android.widget.TabHost;
import android.widget.ArrayAdapter;
import android.widget.ListView;
import android.view.LayoutInflater;
import android.view.ViewGroup;
import android.widget.ImageView;
import android.widget.TextView;
import android.content.Context;
import android.database.Cursor;
import android.support.v4.widget.CursorAdapter;
import android.media.MediaPlayer;
import android.webkit.WebSettings;
import android.webkit.WebView;
import android.webkit.WebViewClient;
import android.view.KeyEvent;

public class DetailForm extends Activity {
    private EditText name = null;
    private EditText author = null;
    private EditText url = null;
    private EditText duedate = null;
    private RadioGroup category = null;
    private BookHelper helper = null;
    private Button save = null;

    private MediaPlayer mp;
    CheckBox chkbox;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.detail_form);

        helper = new BookHelper(this);
        name = (EditText) findViewById(R.id.name);
        author = (EditText) findViewById(R.id.author1);
        url = (EditText) findViewById(R.id.url);
        category = (RadioGroup) findViewById(R.id.category1);

        save = (Button) findViewById(R.id.save);
        save.setOnClickListener(onSave);

        mp = MediaPlayer.create(getBaseContext(), R.raw.sound);
        SharedPreferences sharedPref = PreferenceManager
                .getDefaultSharedPreferences(getApplicationContext());
        boolean isChecked = sharedPref.getBoolean("checked", false);
        if (isChecked == true) {
            if (mp.isPlaying() == false) {
                mp.start();
            }
        } else {

            if (mp.isPlaying() == true) {
                mp.stop();

            }
        }
    }

    @Override
    public void onDestroy(){
        super.onDestroy();
        helper.close();
    }

    @Override
    protected void onStop() {
        super.onStop();
        if (mp.isPlaying() == true){
            mp.stop();
        }
    }

    private View.OnClickListener onSave = new View.OnClickListener() {

        @Override
        public void onClick(View v) {
            // TODO Auto-generated method stub
            String nameStr = name.getText().toString();
            String authStr = author.getText().toString();
            String urlStr = url.getText().toString();
            String dueStr = duedate.getText().toString();
            String catStr = "";

            switch(category.getCheckedRadioButtonId()){
            case R.id.action:
                catStr = "Action";
                break;
            case R.id.mystery:
                catStr = "Mystery";
                break;
            case R.id.thriller:
                catStr = "Thriller";
                break;
            case R.id.romance:
                catStr = "Romance";
                break;
            case R.id.horror:
                catStr = "Horror";
                break;
            case R.id.others:
                catStr = "Others";
                break;
            }

            helper.insert(nameStr,authStr,dueStr,urlStr,catStr);

            finish();
        }
    };

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.main, menu);
        return true;

    }


    public boolean onOptionsItemSelected(MenuItem item) {
        switch (item.getItemId()) {
        case R.id.setting:
            Intent intent = new Intent(DetailForm.this, Settings.class);
            startActivity(intent);

            break;

        }
        return super.onOptionsItemSelected(item);
    }
}

我的主要活动

 package sp.com;

import android.app.Activity;
import android.app.ListActivity;
import android.content.Context;
import android.content.Intent;
import android.content.SharedPreferences;
import android.content.SharedPreferences.Editor;
import android.media.MediaPlayer;
import android.net.Uri;
import android.os.Bundle;
import android.preference.PreferenceManager;
import android.widget.Button;
import android.widget.TextView;
import android.util.Log;
import android.view.Menu;
import android.view.MenuInflater;
import android.view.MenuItem;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.AdapterView;
import android.widget.CheckBox;
import android.widget.EditText;
import android.widget.ImageButton;
import android.widget.RadioGroup;
import android.widget.Toast;
import java.util.ArrayList;
import java.util.List;
import android.app.TabActivity;
import android.widget.TabHost;
import android.widget.ArrayAdapter;
import android.widget.ListView;
import android.view.LayoutInflater;
import android.view.ViewGroup;
import android.widget.ImageView;
import android.widget.TextView;
import android.content.Context;
import android.database.Cursor;
import android.support.v4.widget.CursorAdapter;
import android.media.MediaPlayer;
import android.webkit.WebSettings;
import android.webkit.WebView;
import android.webkit.WebViewClient;
import android.view.KeyEvent;

public class MainActivity extends ListActivity {
    private Cursor model = null;
    private BookAdapter adapter = null;
    private BookHelper helper = null;


    @Override
    public void onCreate(Bundle savedInstanceState) {

        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        helper = new BookHelper(this);

        model=helper.getAll();
        startManagingCursor(model);
        adapter = new BookAdapter(model);
        setListAdapter(adapter);
        }

    @Override
    public void onDestroy(){
        super.onDestroy();
        helper.close();
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu){
        getMenuInflater().inflate(R.menu.option,menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item){
        //TODO Auto-generated method stub
        if(item.getItemId()==R.id.add){
            startActivity(new Intent(MainActivity.this,DetailForm.class));
        }
        return super.onOptionsItemSelected(item);
    }
    class BookAdapter extends CursorAdapter{
        BookAdapter(Cursor c){
            super(MainActivity.this,c);
        }

        @Override
        public void bindView(View row,Context ctxt,Cursor c){
            BookHolder holder = (BookHolder) row.getTag();

            holder.populateFrom(c,helper);
        }

        @Override 
        public View newView(Context ctxt,Cursor c,ViewGroup parent){
            LayoutInflater inflater = getLayoutInflater();
            View row = inflater.inflate(R.layout.row, parent, false);

            BookHolder holder = new BookHolder(row);

            row.setTag(holder);
            return(row);
        }
    }

    static class BookHolder {
        private TextView bookName = null;
        private TextView dueDate = null;


        BookHolder(View row){
            bookName = (TextView) row.findViewById(R.id.bookname);
            dueDate = (TextView) row.findViewById(R.id.duedate);
        }

        void populateFrom(Cursor c, BookHelper helper){
            bookName.setText(helper.getName(c));
            dueDate.setText(helper.getDue(c));
        }
    }
}

最后，我的SQLiteOpenHelper

package sp.com;

import android.content.Context;
import android.content.ContentValues;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;

class BookHelper extends SQLiteOpenHelper {
    private static final String DATABASE_NAME = "books.db";
    private static final int SCHEMA_VERSION = 1;


    public BookHelper(Context context){
        super(context, DATABASE_NAME,null,SCHEMA_VERSION);
    }

    @Override
    public void onCreate(SQLiteDatabase db){
        db.execSQL("CREATE TABLE books_table (_id INTEGER PRIMARY KEY AUTOINCREMENT, "
                + "name TEXT, author TEXT, url TEXT , duedate TEXT , category TEXT);");
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        // TODO Auto-generated method stub

    }

    public Cursor getAll(){
        return(getReadableDatabase().rawQuery(
                "SELECT _id , name , author , url , duedate , category FROM books_table ORDER BY name", null));
    }

    public void insert(String name , String author , String url , String duedate , String category){
        ContentValues cv = new ContentValues();

        cv.put("name",name);
        cv.put("author", author);
        cv.put("url", url);
        cv.put("duedate",duedate);
        cv.put("category",category);

        getWritableDatabase().insert("books_table", "name", cv);
    }

    public String getName(Cursor c){
        return (c.getString(1));
    }

    public String getAuthor(Cursor c){
        return (c.getString(2));
    }

    public String getUrl(Cursor c){
        return (c.getString(3));
    }

    public String getDue(Cursor c){
        return (c.getString(4));
    }

    public String getcat(Cursor c){
        return (c.getString(5));
    }
}

如果您需要有关我的代码的其他信息，请告诉我！谢谢。

此致史蒂夫

Answer 1

使用duedate课程findViewById()内的onCreate()初始化Activity。

Answer 2

使用findViewById（R.id.duedate）初始化oncreate方法中的duedate;

按下＆＃34;应用程序崩溃＆＃34;按键

2 个答案: